IEC 61453-2007 pdf Nuclear instrumentation – Scintillation gamma ray detector systems for the assay of radionuclides – Calibration and routine tests

3.1.4 Routine test 3.1.4.1 Reproducibility tests shall be performed by checking the system response calibration at least once in every week of use with at least one long-lived radioactive checking source with energies that span the region of interest. Correction for radioactive decay of the source since its calibration shall be applied. 3.1.4.2 The response calibration of an idle system when returned to use shall be checked at least semi-annually by using reference sources of radionuclides that span the energy region of interest. 3.1.4.3 The background level of the system shall be measured immediately before and after each batch of samples. The background level shall also be measured periodically, at least once in every week of use. For accurate assays of radioactive materials whose activities are only slightly above background, the system background should be determined using a sufficient number of background readings and using counting times of sufficient length so as to minimize the uncertainty associated with the background count rate. 3.1.4.4 The results of all performance checks shall be recorded in such a way that deviations from the norm will be readily observable. Appropriate action which could include confirmation, repair and recalibration as required shall be taken when the measured values fall outside of predetermined limits.
3.2.5.2 The energy resolution of the system shall be determined at the time of initial installation and checked at least once in every month of use. The energy resolution should be performed with a 1 37 Cs source and a window width less than 1 % of the relevant energy span. The window should be moved in 1 % increments from 1 0 % below the 661 ,6 keV peak to 1 0 % above. The background level shall be determined below and above the peak and an approximately linear baseline under the peak shall be calculated to correct all measured count rates for the respective baseline contributions. FWHM shall be calculated by interpolation on either side. 3.2.5.3 Reproducibility tests shall be performed by checking the efficiency calibration at least once in every month of use with at least one long-lived radioactive checking source with energies that span the region of interest. Correction for radioactive decay of the source since its calibration shall be applied.